DVAS-FHEChain: A Blockchain-Based EHR Privacy Protection Scheme Using Designated Verifier Aggregate Signatures and Fully Homomorphic Encryption

With the widespread adoption of Electronic Health Records (EHRs), ensuring data privacy while enabling efficient sharing and processing has emerged as a critical challenge in healthcare information systems. Existing approaches often struggle to balance stringent security requirements with practical performance needs. To address these challenges, this paper proposes a blockchain-based privacy protection scheme for EHRs that integrates Designated Verifier Aggregate Signatures (DVAS) and Fully Homomorphic Encryption (FHE). In the proposed scheme, healthcare institutions manage EHRs through smart contracts, while FHE is employed to encrypt and protect sensitive medical data used in research. By selectively applying FHE to critical data and minimizing encryption overhead for non-sensitive information, our design significantly enhances computational efficiency and storage performance. Furthermore, the DVAS algorithm minimizes redundant data transmission, ensures data integrity, and restricts signature verification to authorized parties only. Experimental evaluations based on computational time, storage cost, and security analysis demonstrate that the proposed scheme achieves robust security while meeting performance requirements, effectively balancing confidentiality and efficiency in healthcare information systems.